I think you can do these paths as well, not sure. Do you mean some one step to locally override files? I think probably, maybe itd be cool for someone to package it together and make it easy to install whoknows
I agree with @MWM. The files should be placed inside _hd.w3mod/... inside the archive, so it can be imported as a whole folder inside the map and then it will only override the textures for HD players. Of course reducing the size by eliminating unused textures is still the map maker's job.